GEOSCIENCE CANADA Volume 34 Numbers 3/4 September/December 2007 113
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GEOSCIENCE CANADA Volume 34 Numbers 3/4 September/December 2007 113 SERIES through persistence and belief in the construction and management provid- project (a common theme in modern ed by Granby. The operation closed exploration), it was explored and permanently when the copper market brought into production in 1914 by was decimated by the Great Depres- Granby Consolidated Mining, Smelting sion, and whatever was salvageable was and Power Co., Ltd. A large, modern dismantled and shipped out. and self-sufficient town was built Since then, the area has seen around the mine to accommodate, and episodic exploration activities and care for, a large work force and their received scientific studies that have led families, which reached a population of to a modern understanding of the geo- over 2500. Two electrical generating logical setting and origin of the Anyox Great Mining Camps of powerhouses were built, one coal fired copper deposits. The mafic volcanic and the other hydroelectric, to operate and sedimentary host rocks at Anyox Canada 2. the mine, mill and smelter complex are assigned to the Upper Triassic to The History and Geology of that produced blister copper (~99% Upper Jurassic Hazelton and Bowser purity). Over 21.73 million tonnes of Lake groups, respectively. The massive the Anyox Copper Camp, copper ore, at an average recovered sulfide lenses are volcanogenic massive grade of 1.68% Cu, 10.8 g/t Ag and sulfide (VMS) deposits that originally British Columbia 0.20 g/t Au, were treated and smelted formed at, or near the palaeo seafloor, between 1914 and 1935 to produce by hydrothermal processes. The 1 2 Ross Sherlock and Julie Domvile 321 546 tonnes of copper, 206 309 kg hydrothermal system was long-lived (6.6 million oz) of silver, and 3773 kg and precipitated sulfides mainly at the SUMMARY (121 300 oz) of gold. Considering the stratigraphic contact between the mafic The Anyox copper mining camp remoteness of the mine and the tech- volcanic and sedimentary host rocks, played a key role in the early develop- nologies available at the time, this was although some sulfides also occur in ment of northwestern British Colum- a remarkable achievement and an indi- the immediate footwall and hanging- bia. It was discovered in 1889 and cation of the quality of engineering, wall of this contact. An interval of 1Ross Sherlock* Ross Sherlock completed his Ph.D. in 1993 at the University of Waterloo studying the McLaughlin gold mine in California. This was fol- lowed by a post-doctoral fellowship at the Mineral Deposit Research Unit at the University of British Columbia working on volcanogenic massive sulfide deposits in the Canadian Cordillera, including the Anyox deposits. Following this, Ross has worked in the exploration, consulting and government geoscience sectors nationally and internationally. Ross is a director of the Mineral Deposits Division of the Geological Association of Canada, a Councillor for Industry with the Society of Economic Geologists and a member of the editorial board for the Journal of Economic Geologists. In 2003 he was awarded the William Harvey Gross award, by the Mineral Deposits Divi- sion of the Geological Association of Canada, for contributions to the field of economic geology in a Canadian context. *Current address Gold Field Exploration [email protected] 2Julie Domvile Julie Domvile is a freelance writer who has been writing articles for the mineral exploration and mining sector for many years. She is a regular contributor to Mineral Exploration, the quarterly publication of the Association for Mineral Exploration BC (AME BC). Julie is currently working on a book to commemorate the first 100 years of AME BC’s history. [email protected] 114 cherty sedimentary rocks marks the la Grande Dépression, alors que le prix steamships operating along the stormy contact and serves as an important du marché du cuivre s'est effondré, ce BC coast; it produced copper concen- stratigraphic marker for further explo- complexe minier a été fermé et tout ce trates for 22 years, from 1914 until ration. The stratigraphic setting, qui en valait la peine a été démantelé et 1935, from two of four known hydrothermal alteration, style of min- transporté ailleurs. deposits. In spite of its isolation, the eralization and geochemistry of the Depuis lors, la région a été quality of life at the mine was surpris- mafic volcanic rocks are all consistent l'objet d'activité d'exploration et de ingly high; in fact, it was probably with the deposit having formed in a recherches scientifiques épisodiques, ce much better than that experienced by sediment-covered, spreading-ridge set- qui a permis d'en tirer une compréhen- most of the employees before they ting, such as Middle Valley on the sion moderne de son cadre géologique arrived, or later during the Great northern Juan de Fuca Ridge, off the et de l'origine des gisements de cuivre Depression. coast of British Columbia. It is note- d'Anyox. Les roches hôtes d'Anyox worthy that the Hazelton Group also des Groupes de Hazelton et du lac Location and Access hosts the famous Eskay Creek gold Bowser sont des volcaniques mafiques Anyox is situated at sea level, 145 km deposit, which is about 200 km north et sédimentaires datant respectivement north of Prince Rupert near the head of Anyox. Eskay Creek is a precious du Triassique supérieur et du Juras- of Observatory Inlet, an arm of Port- metal-rich variant of the VMS family sique supérieur. Les gisements de land Canal, which is the most northerly and correlations between Anyox and lentilles de sulfures massifs sont des fiord on the British Columbia coast Eskay Creek may stimulate additional sulfures massifs volcanogéniques (Figs. 1, 2). The Portland Canal, which phases of exploration and possibly fur- (SMV) qui se sont formés à l'origine is located 17 km west of the mine, ther chapters in the history of Anyox. près ou sur le fond océanique par des forms the International Boundary processus hydrothermaux. Ce système between BC and the Alaska Panhandle SOMMAIRE hydrothermal qui a fonctionné (Fig. 2). The mine site is situated at Le camp minier cuprifère d'Anyox a longtemps a précipité des sulfures prin- 55° 26’ N and 129° 49’ W, within NTS joué un rôle clé dans le développement cipalement au contact stratigraphique map-sheet 103P/05W. Prior to the du Nord-Ouest de la Colombie-Britan- des roches volcaniques avec les roches introduction of float-equipped aircraft nique. Découvert en 1889, il a été mis sédimentaires hôtes, mais on trouve on the northern coast, it was accessible en production en 1914 par la Granby aussi des sulfures à proximité immédi- only by boat. Consolidated Mining, Smelting and ate du toit et du plancher de ce con- The district lies within a tem- Power Co. Ltd., après qu'on y eut tact. Un intervalle de roches sédimen- perate rainforest and snow is rare at investi une bonne dose de foi et de taire siliceuses constitue un important sea level, but accumulates at higher ele- persistance (thème très actuel de l'ex- marqueur stratigraphique. Le contexte vations where the mine is located. The ploration contemporaine). Une grande stratigraphique, l'altération hydrother- area is within the Boundary Range of ville moderne et autosuffisante a été male, le style de la minéralisation et la the Coast mountains that are character- construite autour de la mine permet- géochimie des roches volcaniques ized by craggy ridges and broad U- tant d'y accueillir et de répondre aux mafiques sont autant de facteurs sou- shaped glaciated valleys. The highest besoins d'une main-d'œuvre consid- tenant l'hypothèse d'un gisement ayant point in the area is Mount Clashmore érable et de leurs familles, une popula- été formé en milieu de crête de fond at 5509 ft (1675 m) which is approxi- tion qui a atteint 2 500 personnes. océanique migrante recouverte de sédi- mately 10 km northwest of Anyox. Deux centrales électriques y ont été ments, comme celle de Middle Valley The tree line is at ~3000 ft (~900 m) construites, l'une au charbon et l'autre de la portion nord de la crête de Juan having mainly pine and alder growth hydraulique. Ces deux centrales per- de Fuca, au large de la côte de Colom- following a devastating fire in 1942. mettaient d'alimenter la mine, l'usine de bie-Britannique. On notera avec traitement et la fonderie, un complexe intérêt que les roches du Groupe de Sources of Information permettant de produire du cuivre à Hazelton sont aussi les roches hôtes du Much of the geological information soufflures d'une pureté de 99 % envi- fameux gisement d'or d'Eskay Creek, has been taken from government-fund- ron. Plus de 21,73 millions de tonnes situé à environ 200 km au nord d'Any- ed geoscience publications, both de minerai de cuivre - à des teneurs ox. Le gisement d'Eskay Creek est une provincial (Carter and Grove 1972; moyennes de 1,68 % de Cu, 10,8 g/t variante riche en métaux précieux de la Grove 1986; Alldrick 1986, 2000) and d'Ag et 0,20 g/t d'Au - y ont été famille de la famille des SMV, et toutes federal (Evenchick and Holm 1997; traitées entre 1914 et 1935, ce qui a corrélations établies entre Anyox et Evenchick et al. 1997; Evenchick and donné 321 546 tonnes de cuivre, 206 Eskay Creek pourraient relancer McNicoll 2001). Three graduate theses 309 kg (6,6 millions d'onces) d'argent, d'autres épisodes d'exploration, et have been completed on the deposit et 3 773 kg (121 000 onces) d'or.